一些关于标准输入输出流的控制符的知识

#include<iostream>
#include<iomanip>
using namespace std;
int main()
{
	double a=123.456789012345;
	cout<<a<<endl;
	cout<<setprecision(9)<<setw(20)<<setiosflags(ios::right)<<a<<endl;
	cout<<setiosflags(ios::fixed)<<setprecision(9)<<a<<endl;
	cout<<setiosflags(ios::scientific)<<a<<endl;
	cout<<setiosflags(ios::scientific)<<setprecision(4)<<a<<endl;
	return 0;
}